Recently, image decolorization is widely used in various areas such as monochromatic printing, monochromatic medical displays, and pattern recognition. On the other hand, color image enhancement is commonly found in medical image enhancement, defect detection, and visual inspection and interpretation. Such demands in the market push a lot of researchers in image processing devoting to a variety of researches in these application areas.
U.S. Pat. No. 7,151,858 provides an apparatus and a method for correcting the sharpness of an image signal, using a Haar Wavelet transform and a difference between pixel values adjacent to the edge of the image signal to be corrected while reducing the occurrence of overshoot and undershoot at the edge of the image signal. The apparatus includes an edge detector for detecting data on the edge of the image signal, by performing a multi-stage Haar Wavelet transform on the image signal, a gain detector for detecting a gain for correcting the image edge, a pixel value detector for detecting a corrected pixel value regarding the edge data at a position to be corrected by performing an operation on the edge data, at least one pixel adjacent to the edge data, and the gain, and an image signal generator for generating an image whose edge is formed based on the corrected pixels.
US20060013504 discloses a method for image enhancement including performing a multi-resolution decomposition of an input image, thereby generating multi-resolution transform components associated with different image scales, comprising at least first and second image scales. A multi-resolution reconstruction is performed to generate an enhanced image by applying filter coefficients to the multi-resolution transform components, such that different, first and second filter coefficients are respectively applied to the multi-resolution transform components that are associated with the first and second image scales. The decomposition is typically performed using a forward transformation filter, and the reconstruction uses a reverse transformation filter, which is not necessarily an inverse of the forward transformation filter. U.S. Pat. No. 7,295,695 discloses a method of detecting a defect in a reticle or wafer using wavelet transforms to differentiate between real defects and pattern noise. A first image and a second image of a sample are aligned. A wavelet transform is obtained of the difference between the images. The wavelet transformed difference image is filtered to distinguish between real defects and pattern defects.
Nevertheless, the color contrast and detail lost in the luminance is frequently found during the image processing in the conventional methods.
Consequently, there is an unmet need to an image processing method, which is effective in recovering the color contrast and detail lost in the luminance so as to improve sharpness and fine details in both enhanced grayscale and color images.